Wire rope, simply stated, consists of a number of wires twisted together to form a strand, a number of these strands then being twisted together helically and symmetrically to form a rope made of wire. This "stranding" of many small wires together forms a rope of a given aggregate sectional area, which when compared to a single bar of steel having the same sectional area, is of much greater strength and flexibility.
While wire rope is recognized as an immensely applicable haulage device, it is only as strong as its weakest link. This link, in quite a number of cases, is the spliced area on the wire rope. When such wire rope slings fail, they do so at the splice, unless the rope has been kinked or cut elsewhere. The industry has used swage sleeves for protecting this weakened area as well as fortifying it to the extent possible.
Under present practice, considerable time is spent forming and fixing eyes or splices on the end of wire ropes. Among the various alternative methods of formation are the "farmer's eye method", the "flemish eye method" and the "torpedo loop locks method". In all cases, however, the wire rope end is threaded through the small end of a swage sleeve. The end of rope is unlayed such that two groups of wires are formed. One group generally has the same number of strands as the other although this will obviously not be so with wire ropes having an odd number of strands. The two groups of strands are crossed to form a loop of the desired size and the two strands are layed back upon the loop such that they terminate at the point where the two strands originally separated. Once this is accomplished, the swage sleeve is manually pulled onto the "Y-shaped" portion of the eye or sling. The sleeve is then swaged or pressed onto the wire rope under a relatively large load derived from a 500 to 600 ton press. The swaged sleeve then holds the eye or sling from slipping when a load is applied to the sling.
The major problem in this method usually comes in the attempt to manually slide the swage sleeve over the "Y-shaped" portion of the wire rope. Each employee employs a different method to assemble the sleeve over the wire rope splice. In general, after the eye or sling has been formed, the employee must clamp the rope in a vice, hold the rope ends of the splice in position, and at the same time pull the sleeve onto the rope. The employee then unclamps the rope from the vice and goes onto the swaging operation at the large swaging press.
There are several problem areas in the present procedure. For instance, manually forcing the sleeve over the wire rope and its loose ends is time consuming and awkward. Difficulties in this area arise in getting the ends started into the swage sleeve. If the wires are not spread out properly around the rope, it can be difficult to pull the sleeve onto the rope. In this operation, it is possible to pinch a finger or get a puncture wound while holding and pulling the sleeve onto the rope. Furthermore, it is also possible that the sleeve will not always be pulled far enough onto the rope to make a proper connection. How far the rope enters the sleeve is left to the judgment of the employee unless he carefully measures the distance moved. Usually the employee does not take the time to measure the rope movement into the sleeve and accordingly, a weakened splice and swage results.
In the currently-employed method, the wire rope must be placed in a vice to clamp the same. This takes time and can be awkward if a special jaw has not been installed on the vice to protect the rope. It should be noted in this regard that rope damage cannot be tolerated under any circumstance. Excessive pinching or clamping can result in a weakened point on the rope and resulting in a rejection if the product is subject to a quality control. If quality control is not followed, the damaged wire rope may result in a greatly reduced strength limit to a point wherein the specific strength tolerances of the individual wire rope may be exceeded during its usage, and breakage and injury may result.